In positioning transducers, such as magnetic read/record heads, with reference to data tracks on one or more magnetic disks, data processing systems utilize techniques which detect position information which has been previously recorded on a selected magnetic disk or drum. Exemplary systems suggested by the prior art include that disclosed in U.S. Pat. No. 3,534,344, "Method and Apparatus for Recording and Detecting Information", issued to G. R. Santana on Oct. 13, 1970, and that disclosed in U.S. Pat. No. 3,893,180, "Transducer Positioning System", issued to W. A. Braun and D. S. Dunn on July 1, 1975.
The position information in such systems consists of separately identifiable magnetic recordings occurring on adjacent tracks of the magnetic disk surface. The position information is sent by a servo transducer which produces a servo signal containing responses to each identifiable recording. A transducer position is defined when the signal strength of each of the responses is exactly equal.
In a specific implementation of such a system, such as shown in the above-mentioned Braun and Dunn patent, the signal strengths of each response are evaluated by a novel detection system which first identifies the responses within the servo signal. The peak amplitudes of the responses are thereafter separately measured and separate signals are produced which are indicative of the measured peak amplitudes. These separate signals are thereafter combined so as to indicate whether the signal strength of either response dominates over the other.
In the previously used prior art systems, adjustment must be continuously made as by using appropriate potentiometer adjustment circuitry in order to assure that offset errors which are present in each of the signals and which subsequently arise in the peak detection process are appropriately taken into account. In order to do so, such systems must utilize highly accurate resistors in the peak detection circuitry thereof, which resistors must be hand selected in order to assure that they have desired matching values for reducing the peak detector offset errors as much as possible.
Apart from the expense of such hand selection, the requirement for continual adjustments in the field hampers the use thereof in many applications and it is desirable to provide a system in which the offset errors can be automatically eliminated without the need for the system operator to continually adjust the system operation for such purpose.